Will a iron-projectile fired into a barrel-mounted Gauss-coil gain speed?

I was wondering if a projectile can be introduced to a Gauss-field and pick up kinetic energy when initial speed before coil were about 1000 fps.
Or if the ironmass have to be initially fired from the same discharge\stream of flux to gain any speed.
And least, would the Gauss-field slow the mass down if the timing was off? (a hz-question?)

The more polit.correct definition of the question within, I belive consist in if wether or not the velocity\kinetic energy of an iron mass would gain more kinetical energy from a Gauss-coil induced force of pull?

The initial kinetic energy from exhausting gases\an airgun's pressurized aircushin in a barrel only create an accel.force when confined in a barrel, and will loose energy when leaving muzzle\disperced.

Any gain of speed will only happen if the *well-timed* coil-induced Gaussian force of pull exceeds the initially force of acceleration released upon primary firing.
More; Will it be possible to carry the amount of batteries needed for the capacitor to keep the required surge discharging in loading-phase long enough for the "Flux-affaire" to peak?